Sergei Magnitsky was our attorney, and friend, who died under excruciating circumstances in a Moscow pre-trial detention center on Nov. 16, 2009. His story is one of extraordinary bravery and heroism, and ultimately tragedy. It is also a story about how Stalinism and the gulags are alive and well in Russia today.

Ultimately Sergei died for a principle -- he died because believed in the rule of law in Russia. When he stumbled upon an enormous fraud against his clients and the Russian government, he thought he was simply doing the right thing by reporting it. He never imagined that he would die for his efforts.

The precise circumstances of his death are still unclear. We do know Sergei died suddenly at the age of 37, after an 11-month detention. At first, the detention center where he died said the cause of his death was a rupture to his abdominal membrane, but on the same day the prison officials changed their story, saying he had died of a heart attack. They refused his family's request to conduct an independent autopsy. His diaries are reported to be missing.

Because Sergei is no longer alive to tell his story, I feel it is my duty to tell it for him. I am not a writer or a journalist, but a fund manager at Hermitage Capital Management. I ran what was the largest investment fund in Russia. Sergei was our Moscow-based outside counsel who worked for the American law firm Firestone Duncan.

Sergei wasn't involved in politics, he wasn't an oligarch, and he wasn't a human rights activist. He was just a highly competent professional -- the kind of person one could call up as the workday was finishing at 7 p.m. with a legal question and he would cancel his dinner plans and stay in the office until midnight to figure out the answer. He was a smart and honest man working hard to better himself and to make a good life for his wife and two kids.

The tragic events that led to his death began on June 4, 2007. That day, 50 police officers from the Moscow Interior Ministry raided Hermitage's and Firestone Duncan's offices, under the pretense of a tax investigation into a Hermitage client company. There was no reason for the raid, as the company they were investigating was regularly audited by the tax authorities, and they never found any violations.

In the course of the raid, the police officers took away all the corporate seals, charters, and articles of association of all of the fund's investment companies -- none of which had anything to do with their search warrant. The significance of these seizures would only become apparent later.

In mid-October 2007, we got a telephone call from a bailiff at the St. Petersburg Arbitration Court inquiring about a judgment against one of the fund's Russian companies. It was a strange call because the company had never been to court and we knew nothing about any lawsuits or judgments in St. Petersburg.

We called Sergei right away and asked him to look into this call. After researching the situation, he came back to us with shocking news. He discovered that our investment companies had been sued by shell companies that we had never done any business with based on forged and backdated contracts. He also discovered that the fund's companies had been represented by lawyers that the fund had never hired, and who proceeded to plead guilty to all the liabilities in the forged contracts. As a result, the fund's companies were hit with court judgments for hundreds of millions of dollars. On top of that, the fund's companies had been fraudulently re-registered in the name of a company owned by a man convicted of manslaughter.

Most shockingly, when Sergei analyzed the forgeries and fraudulent re-registrations, he was able to prove that they could have only been executed with the documents seized from our offices by the Moscow Interior Ministry.

On the back of Sergei's discoveries, in early December 2007, we filed six 255-page complaints outlining all the details of the frauds and the names of the police officers involved. The complaints were filed with the heads of the three main law enforcement agencies in Russia. However, instead of investigating, they passed the complaints straight back to the specific police officers named as conspirators. Those officers then personally initiated retaliatory criminal cases against Hermitage employees.

At this point, Sergei was becoming visibly angry. Sergei wasn't a dispassionate lawyer like many we have encountered in the past. He was our advocate in the truest sense of the word.

By the summer of 2008 it still wasn't clear why the police would be involved in such a complicated scam against us. If the intention was to steal the fund's assets in Russia, they had failed because, by the time our companies were stolen, the assets had been safely moved outside the country.

To help us find the answer, Sergei sent out more than 50 letters to different tax authorities and registration offices requesting information on our stolen companies. Almost no one replied, but on June 5, 2008, Sergei received a letter that broke the case wide open.

According to the letter, which was from tax authorities in Khimki, a suburb of Moscow, our stolen companies had been re-registered in Khimki, and had opened bank accounts at two obscure Russian banks. Once we learned about the banks, everything started to make sense. At those banks, Sergei found a spike in deposits exactly equal to the taxes that the Hermitage Fund companies had paid in 2006. Apparently, the people who stole our companies did so to fraudulently obtain $230 million that the Hermitage Fund companies had paid in taxes in 2006 by claiming that the sham court judgments had wiped out their profits.

The refund of "overpaid taxes" -- the largest in Russian history -- had been granted by the Moscow tax authorities in two days on Dec. 24 2007. The date of the wire transfer showed that it was carried out in total disregard of the complaints the fund filed to the Russian authorities three weeks earlier.

Sergei didn't start out as an anticorruption crusader, but when corruption stared him in the face, he felt compelled to do something about it. In July 2008, Sergei helped us prepare a detailed criminal complaint about the stolen tax money, which was filed with seven different Russian government agencies.

After our complaints were filed, the Interior Ministry officers who were involved in the fraud retaliated by opening criminal cases targeting all the lawyers who represented the fund. The pressure became so intense that six of our lawyers from four different law firms were forced to either leave the country or to go into hiding.

The one lawyer who didn't leave Russia was Sergei. In spite of the clearly malicious activity by the police, he was sure that he was safe because he had never done anything wrong or illegal. He believed that the law of Russia would protect him.

His belief in justice was so strong that he went on to do something many people would be petrified to even consider. On Oct. 7, 2008, he went to the offices of the Russian State Investigative Committee (the Russian equivalent of the FBI) and testified against two officers of the Interior Ministry, Lt. Col. Artem Kuznetsov and Maj. Pavel Karpov, for their involvement in the theft of $230 million. It was an enormously brave move, and we feared for him that day. Amazingly, Sergei was the only person who wasn't worried.

Just over a month later, three officers who directly reported to Kuznetsov went to Sergei's apartment at 8 a.m. and arrested him. He was charged with being the director of two Hermitage Fund companies that allegedly underpaid taxes in 2001. He was arrested even though the companies had clean audits and Sergei had had no involvement with either of the companies in 2001. However, the law didn't matter. The investigators had other plans for Sergei.

Sergei was brought to Pre-Trial Detention Center No. 5 in Moscow, but within months he was transferred to a temporary detention facility with much harsher conditions, and then he was moved seven times between four more detention centers until he was moved to Matrosskaya Tishina prison.

Each move was progressively worse, and we started to get word that he was being kept in very harsh conditions. We heard about him being kept with eight other inmates in prison cells that only had four beds so they had to sleep in shifts. We heard about how the prison authorities never turned the lights off at night so even if he got a bed, it was almost impossible to sleep. Most disturbing of all, we got news that he was starting to lose weight precipitously. Since his arrest, he had lost 40 pounds.

On July 1, 2009, at Matrosskaya Tishina, Sergei was diagnosed with pancreatitis and gallstones. He was told that he should be monitored closely, and that he would need a repeat examination and surgery within a month. As he was preparing for a follow-up visit to the medical center, on July 25, 2009, he was abruptly transferred to Butyrka prison, a maximum security facility known to be one of the toughest in Russia.

At Butyrka, Sergei's condition deteriorated sharply, and he developed excruciating stomach pains. He repeatedly asked the prison authorities, prosecutors, investigators, and the courts for medical attention, and he was repeatedly denied it by all of them. At one point the pain became so intense that he couldn't even lie down. His cellmate banged on the door for hours screaming for a doctor. When one finally arrived, he refused to do anything for Sergei, telling him he should have obtained medical treatment before his arrest.

We did what we could do to help him. We testified in front of the U.S. Congress about Sergei; we asked the U.S. State Department and the British Foreign Office to bring his case up with the Russian Foreign Ministry; we reached out to the professional associations; and we constantly provided information to journalists to write about his situation. But none of it mattered within Russia. While we were lobbying from the outside, they were putting more and more pressure on Sergei from the inside.

His tormentors wanted to pressure him to withdraw his testimony against the police officers and make false statements against himself and his client, the Hermitage Fund. Most cynically, they specifically wanted him to take responsibility for the theft of $230 million that they had been stolen from the state. As a lawyer and someone who believed in justice, there was no way he would be pressured into perjuring himself no matter how much pain he had to endure. Instead, he wrote even more complaints documenting the horrific torture he was being subjected to.

The more Sergei complained, the more the pressure increased. He was moved to cells where sewage would spew up from the hole in the floor that served as the toilet. He was put in cells with no glass in the windows to protect the inmates from the frigid Russian weather. The prison authorities denied him any opportunity to shower, or simply access hot water. Worst of all they denied him any visits from his wife or mother, or even the possibility to speak to his two young children on the telephone for the 11 months he was in detention, which must have been truly heartbreaking for a man so committed to his family.

Despite all this and more, he was never broken. During his 358 days in detention, Sergei and his lawyers filed more than 450 complaints documenting all of the breaches of Russian law, and the violations of his human rights. He wrote on behalf of himself and on behalf of other detainees. Few people could have managed such a prodigious effort while being subjected to such physical torment. Sergei didn't have access to an office, library, or a computer. He managed to do all this without even a table to write on. Each time Sergei filed a complaint, it was rejected or simply ignored, but each defeat just served to make him more indignant and determined. He was always the consummate professional. There was never any emotion in his complaints, even after all the torture he endured. They were crisp and exact.

Throughout this ordeal, Sergei stood true to his principles -- refusing to perjure himself and make false statements against himself and his client -- no matter what new suffering was devised for him.

In the end, Sergei died suddenly in prison on Nov. 16, 2009. He entered prison a healthy 36-year-old man, and 11 months later he was dead. Many questions remain, but what is clear is that the abuses he suffered during his year in detention ultimately caused his death.

One can never judge the true character of a person until they are faced with extreme adversity. Most people, if faced with a far lesser challenge than Sergei, would have given in. But for Sergei, his integrity and honor were more important than any physical pain he was suffering. Sergei was an ordinary man who became an extraordinary hero. If we all could only show a fraction of the bravery and fortitude Sergei did, the world would be a much better place. Sergei, his heroic fight, and the ideals he stood for must never be forgotten.

God bless Sergei and his family.

William Browder is the founder and CEO of Hermitage Capital Management, which was once the largest investment firm in Russia.